This invention relates generally to pressure relief valves, and more particularly, to pressure relief valve assemblies for use in pneumatic pipeline plugs.
Pressure relief devices are typically designed to prevent over pressurization of a system by allowing the escape of a fluid, such as gas or liquid. Pressure relief valves are typically designed to relieve fluid pressure from a system at a specified pressure limit and to reclose when the system pressure returns to that pressure limit.
Pressure relief valves are most often designed for specific applications and uses in constant or fixed volume systems. In relief valves used in flexible systems and those in systems having the potential of repeated use it is of increased importance to provide valve reliability. For example, repeatability of cracking and reseating pressures are important in these pressure relief valve structures.
Pneumatic plugs are monitored during inflation and use with a pressure gauge, the valve of this invention further ensures the integrity of the pneumatic plug. Although pressure relief structures have been designed in the past for use in pneumatic plugs, they have typically been designed to function in cooperation with other elements of the plug body itself. These prior art valve structures and the use of known pressure relief valve designs have been found to yield low fluid flow characteristics, inconsistent reseating results, to be difficult to adjust and expensive to manufacture.
The pressure relief valves of this invention are designed to be incorporated in a flexible pressurized system and particularly in pneumatic pipeline plugs. Pneumatic plugs are used in the plumbing industry, for example, to seal pipelines and other conduits. These plug devices expand upon the introduction of a pressurized fluid, such as air or water, to seal against the interior wall of the pipe. These pneumatic plugs are flexible pressurized systems which operate at relatively low fluid pressure ranges. The relief valve structures, therefore, require specific requirements including reliability, repeatability, economy and ease of manufacture.
Despite the need for a functional and inexpensive pressure relieve valve device in the art which can be incorporated into pneumatic plugs, and which overcomes the limitations and problems of the prior art, none insofar as is known has been proposed or developed.
Accordingly, it is an object of the present invention to provide an efficient and inexpensive pressure relief valve for pneumatic plugs. The pressure relief valve of this invention has a structure that provides a large area for fluid flow in a relatively small diameter valve size and provides repeatable reseat characteristics. Particularly provided is a relief valve structure which is integral with an end cap assembly for pneumatic test plugs, which can be preset during manufacture and assembly and which is tamper resistant in the field.